The aims of this study are to determine the characteristics of inhibition of pancreatic exocrine secretion by the beta 2-adrenergic agonist terbutaline in dogs and man, and to determine whether pancreatic secretory inhibition by this agent can alter the course of radiation enteritis in dogs. Pancreatic exocrine function will be assessed in dogs surgically prepared with chronic pancreatic and gastric fistulae. This model will be used in several series of experiments designed to assay the inhibition of pancreatic secretion after administration of terbutaline, either orally, subcutaneously, or intravenously. When the doses of terbualine that produce maximal inhibition of pancreatic secretion have been established by these experiments, we will study the effects of this maximal pancreatic exocrine inhibition on the course of radiation enteritis in dogs. In addition, using the information obtained from the experiments regarding the characteristics of pancreatic secretory inhibition by terbutaline in dogs, a series of experiments will be carried out using normal human volunteers to determine whether terbutaline will also inhibit the human exocrine pancreas. It is hoped that this series of experiments will help to develop a clinically safe and useful treatment for patients in whom it may be necessary to reduce pancreatic exocrine function.